Remove typing constraint

Author: hansthen

folium/map.py

@@ -433,7 +433,7 @@ def render(self):
             self.add_child(self.SetIcon(marker=self, icon=self.icon))
         super().render()
 
-    def set_icon(self, icon: Union[Icon, "CustomIcon", "DivIcon"]):
+    def set_icon(self, icon):
         super().add_child(icon)
         self.icon = icon